王 磊,王魯民,馮春雷,張 勛,周愛(ài)忠,張 禹,劉永利,齊廣瑞
(中國(guó)水產(chǎn)科學(xué)研究院東海水產(chǎn)研究所,農(nóng)業(yè)部遠(yuǎn)洋與極地漁業(yè)創(chuàng)新重點(diǎn)實(shí)驗(yàn)室,上海 200090)
基于導(dǎo)流板形狀變化的雙開(kāi)縫曲面網(wǎng)板水動(dòng)力性能研究
王 磊,王魯民,馮春雷,張 勛,周愛(ài)忠,張 禹,劉永利,齊廣瑞
(中國(guó)水產(chǎn)科學(xué)研究院東海水產(chǎn)研究所,農(nóng)業(yè)部遠(yuǎn)洋與極地漁業(yè)創(chuàng)新重點(diǎn)實(shí)驗(yàn)室,上海 200090)
開(kāi)展風(fēng)洞試驗(yàn)研究導(dǎo)流板形狀變化對(duì)雙開(kāi)縫曲面網(wǎng)板水動(dòng)力性能的影響,以優(yōu)化網(wǎng)板導(dǎo)流板結(jié)構(gòu),提高雙開(kāi)縫曲面網(wǎng)板的水動(dòng)力性能。試驗(yàn)設(shè)計(jì)4種導(dǎo)流板形狀的網(wǎng)板模型,分別為矩形、扇形、凸梯形和凹梯形,4塊網(wǎng)板模型的基本結(jié)構(gòu)參數(shù)相同,展弦比2.5,葉板的曲率12%,雙層導(dǎo)流板的預(yù)設(shè)角度30°和25°,主面板角度12°,試驗(yàn)風(fēng)速28 m·s-1,沖角(α)范圍0°~70°,模型安裝于塔式六分量機(jī)械-應(yīng)變天平的立柱上,分別對(duì)網(wǎng)板所受到的阻力、升力和力矩進(jìn)行測(cè)量。結(jié)果顯示:在網(wǎng)板升力系數(shù)方面,4塊網(wǎng)板模型的最大升力系數(shù)為Cy(凸梯形)>Cy(矩形)>Cy(扇形)>Cy(凹梯形),具有凸梯形結(jié)構(gòu)的網(wǎng)板模型的最大升力系數(shù)較高,為1.946(α=47.5°);在網(wǎng)板阻力系數(shù)方面,在沖角為 30°時(shí),Cx(扇形)>Cx(矩形)>Cx(凹梯形)>Cx(凸梯形),具有凸梯形結(jié)構(gòu)的網(wǎng)板模型阻力系數(shù)較低;4塊網(wǎng)板模型的最大升阻比關(guān)系為Cy/Cx(凸梯形)>Cy/Cx(矩形)>Cy/Cx(扇形)>Cy/Cx(凹梯形),具有凸梯形結(jié)構(gòu)的網(wǎng)板模型最大升阻比較高,為 7.486(α=30°);在穩(wěn)性對(duì)比方面,扇形導(dǎo)流板結(jié)構(gòu)網(wǎng)板模型穩(wěn)性較好,Cm絕對(duì)值與Cp變異系數(shù)分別為0.061和5.43%。試驗(yàn)表明,具有凸梯形導(dǎo)流板的雙開(kāi)縫曲面網(wǎng)板可以產(chǎn)生較大的升力,且阻力較小,具有良好的工作效果;具有扇形導(dǎo)流板的雙開(kāi)縫曲面網(wǎng)板穩(wěn)性較高。試驗(yàn)結(jié)果可為拖網(wǎng)網(wǎng)板的結(jié)構(gòu)優(yōu)化設(shè)計(jì)提供參考。
網(wǎng)板;風(fēng)洞試驗(yàn);水動(dòng)力性能;導(dǎo)流板
網(wǎng)板是拖網(wǎng)的重要屬具,連接于拖網(wǎng)網(wǎng)口兩側(cè),在拖曳前行時(shí)靠水流產(chǎn)生水平作用力擴(kuò)張網(wǎng)口。配備水動(dòng)力性能優(yōu)良的網(wǎng)板可以提高捕撈生產(chǎn)效率,達(dá)到增產(chǎn)降耗的目的。通過(guò)調(diào)整網(wǎng)板的型式與結(jié)構(gòu)參數(shù)以優(yōu)化其水動(dòng)力性能是目前漁業(yè)裝備的一個(gè)研究方向,國(guó)外如日本、澳大利亞等漁業(yè)發(fā)達(dá)國(guó)家針對(duì)網(wǎng)板水動(dòng)力性能均開(kāi)展過(guò)研究,如福田賢吾等[1-2]對(duì)不同展弦比的立式曲面網(wǎng)板的水動(dòng)力特性進(jìn)行研究,并通過(guò)改變前后翼間隔和交錯(cuò)角,對(duì)雙翼型網(wǎng)板的水動(dòng)力性能進(jìn)行了研究;松田皎等[3]對(duì)展弦比1.67、彎曲度14.1%、上反角 12°、后退角15°的立式 V型曲面網(wǎng)板水動(dòng)力特性進(jìn)行了研究;樸倉(cāng)斗等[4]對(duì)不同展弦比的矩形網(wǎng)板水動(dòng)力性能進(jìn)行了研究;BROADHURST等[5]開(kāi)展了網(wǎng)板在拖網(wǎng)中的應(yīng)用性能對(duì)比研究;SALA等[6]對(duì)特性結(jié)構(gòu)網(wǎng)板開(kāi)展了模型與海上實(shí)物網(wǎng)板的試驗(yàn)對(duì)比。中國(guó)自20世紀(jì)80年代起,科研人員也進(jìn)行了網(wǎng)板水動(dòng)力性能的相關(guān)研究,如張勛等[7]、王錦浩等[8]分別對(duì)V型曲面網(wǎng)板水動(dòng)力性能開(kāi)展試驗(yàn),分析網(wǎng)板不同結(jié)構(gòu)參數(shù)對(duì)其水動(dòng)力性能的影響;王明彥等[9]考察了上反角、后退角和展弦比對(duì)立式V型曲面網(wǎng)板水動(dòng)力性能的影響;徐寶生等[10]開(kāi)展了矩形Ⅴ型曲面網(wǎng)板和Ⅴ型網(wǎng)板生產(chǎn)性對(duì)比試驗(yàn)。目前的研究主要集中于網(wǎng)板不同型式結(jié)構(gòu)水動(dòng)力性能的差異,但在系列性優(yōu)化改進(jìn)網(wǎng)板結(jié)構(gòu)等方面尚需開(kāi)展相關(guān)基礎(chǔ)研究[11-12]。進(jìn)入21世紀(jì)后我國(guó)的近海與遠(yuǎn)洋漁業(yè)發(fā)展更為迅速,目前仍有較多的作業(yè)漁船及漁具裝備較為落后,還停留在十幾年前的裝備水平,網(wǎng)板的型式結(jié)構(gòu)較為簡(jiǎn)單,需要進(jìn)一步改進(jìn)以提高其性能[13-14]。網(wǎng)板的性能優(yōu)化可以通過(guò)改變網(wǎng)板的結(jié)構(gòu),包括展弦比、開(kāi)縫、V型板面折角、葉板曲率與角度等。例如,多翼型網(wǎng)板可提高網(wǎng)板穩(wěn)性[15];立式V型曲面等開(kāi)縫網(wǎng)板可以更好的提升網(wǎng)板的擴(kuò)張性能[7-9];橢圓型開(kāi)縫網(wǎng)板相比矩形平面網(wǎng)板可以更好的適應(yīng)劣質(zhì)海底作業(yè)[16-17],調(diào)整網(wǎng)板的葉板形狀可以改善網(wǎng)板的水動(dòng)力性能,導(dǎo)流板作為網(wǎng)板前緣的導(dǎo)流裝置,通過(guò)改變網(wǎng)板的流態(tài)以優(yōu)化網(wǎng)板的水動(dòng)力性能[18-19],導(dǎo)流板的形狀變化同樣會(huì)對(duì)流態(tài)產(chǎn)生影響,目前此類相關(guān)研究還比較少,本研究選取目前國(guó)內(nèi)外應(yīng)用較多的雙開(kāi)縫曲面網(wǎng)板結(jié)構(gòu)設(shè)計(jì)模型并開(kāi)展風(fēng)洞試驗(yàn),通過(guò)變化網(wǎng)板導(dǎo)流板的形狀對(duì)比其水動(dòng)力性能差異,篩選具有較優(yōu)水動(dòng)力性能的導(dǎo)流板形狀結(jié)構(gòu),以期為網(wǎng)板整體性能的優(yōu)化研究提供參考。
試驗(yàn)網(wǎng)板模型為雙開(kāi)縫矩形曲面網(wǎng)板,網(wǎng)板的葉板由雙層導(dǎo)流板和一層主面板組成。本試驗(yàn)網(wǎng)板模型結(jié)構(gòu)設(shè)計(jì)基于大展弦比中層拖網(wǎng)網(wǎng)板,網(wǎng)板面積一般在8~12 m2,試驗(yàn)?zāi)P驮诨窘Y(jié)構(gòu)參數(shù)一致的前提下簡(jiǎn)化結(jié)構(gòu)并等比例縮小,僅對(duì)導(dǎo)流板的葉片形狀進(jìn)行變化。網(wǎng)板模型的結(jié)構(gòu)及參數(shù)說(shuō)明見(jiàn)圖1。
試驗(yàn)用4塊網(wǎng)板模型的展弦比為2.5,網(wǎng)板模型投影面積均為0.160 m2,且各模型對(duì)應(yīng)導(dǎo)流板及主面板的投影面積相同,其它具體參數(shù)見(jiàn)表1,對(duì)4塊網(wǎng)板模型分別編號(hào)為1、2、3、4。制成的網(wǎng)板模型實(shí)物材質(zhì)為鋼,表面涂漆(圖2)。
試驗(yàn)風(fēng)洞為南京航空航天大學(xué)NH-2風(fēng)洞,該風(fēng)洞為串置雙試驗(yàn)段閉口回流風(fēng)洞,本次試驗(yàn)在小試驗(yàn)段中進(jìn)行,小試驗(yàn)段主要技術(shù)性能為:6 m(長(zhǎng))×3 m(寬)×2.5 m(高),進(jìn)口截面積為7.18 m2,最大風(fēng)速可達(dá)到90 m·s-1,最小穩(wěn)定風(fēng)速為5 m·s-1。
本次測(cè)力試驗(yàn)采用塔式六分量機(jī)械-應(yīng)變天平進(jìn)行測(cè)量,試驗(yàn)?zāi)P桶惭b示意圖見(jiàn)圖3。
試驗(yàn)采用的數(shù)據(jù)采集處理系統(tǒng)由前置放大器、4臺(tái)聯(lián)網(wǎng)計(jì)算機(jī)系統(tǒng)組成。
圖1 雙縫矩形曲面網(wǎng)板模型結(jié)構(gòu)及對(duì)應(yīng)參數(shù)Fig.1 Structure and parameters of double-slit rectangular cambered otter board model注:L:網(wǎng)板翼弦長(zhǎng);b:網(wǎng)板翼展長(zhǎng);e:模型支點(diǎn)中心到前緣距離;B1,B2:導(dǎo)流板;A:主面板;γ1,γ2:導(dǎo)流板的角度;β:主面板的角度Note:L:chord;b:span;e:distance from the leading edge to the center pivot;B1,B2:deflector;A:main-panel;γ1,γ2:angle of the deflector;β:angle of themain panel
表1 網(wǎng)板模型主尺度及結(jié)構(gòu)參數(shù)說(shuō)明Tab.1 Dimension and structure parameters of otter board models
圖2 4塊網(wǎng)板模型及設(shè)計(jì)正視圖Fig.2 Four otter board models and front view of design注:網(wǎng)板模型1、2、3、4結(jié)構(gòu)參數(shù)見(jiàn)表1;B1,B2:導(dǎo)流板;A:主面板Note:The structure parameters of4 otter-board models are shown in Tab.1;B1,B2:deflector;A:main-panel
圖3 網(wǎng)板模型風(fēng)洞試驗(yàn)安裝示意圖Fig.3 Installation instruction of otter board model in w ind tunnel
1.3.1 試驗(yàn)?zāi)P拖嚓P(guān)參數(shù)定義
網(wǎng)板模型在風(fēng)洞中的試驗(yàn)安裝情況可見(jiàn)圖3。4塊網(wǎng)板模型按順序依次安裝到風(fēng)洞中的六分量機(jī)械天平底座上,當(dāng)風(fēng)速達(dá)到28 m·s-1時(shí)(室溫為20℃),沖角由0°~70°進(jìn)行轉(zhuǎn)動(dòng),其中在沖角0°~50°區(qū)間,每間隔 2.5°為一個(gè)測(cè)錄數(shù)據(jù)點(diǎn),沖角50°過(guò)后,每間隔5°為測(cè)錄數(shù)據(jù)點(diǎn),共計(jì)25組數(shù)據(jù),包括阻力系數(shù)Cx、升力系數(shù)Cy、俯仰力矩系數(shù)Cm與壓力中心系數(shù)Cp。
試驗(yàn)?zāi)P驮陲L(fēng)洞試驗(yàn)段中相關(guān)參數(shù)定義如圖4所示。圖4中0點(diǎn)為力矩參考點(diǎn),即模型底部的打孔處。在試驗(yàn)過(guò)程中,模型的阻力由天平沿X軸方向的力提供,升力由天平沿Z軸方向的力提供,俯仰力矩由天平繞Z軸方向的My元提供。
圖4 試驗(yàn)?zāi)P驮陲L(fēng)洞中相關(guān)參數(shù)定義示意圖Fig.4 Param eter definition diagram of testmodel in w ind tunnel注:FL:升力;FD:阻力;M:俯仰力矩;V:風(fēng)速Note:FL:lift;FD:drag;M:pitch moment;V:wind speed
本期試驗(yàn)風(fēng)速取V=28 m·s-1,此時(shí)雷諾數(shù)(粘性系數(shù)),處于網(wǎng)板模型試驗(yàn)的自動(dòng)模型區(qū)[7,20]。
1.3.2 試驗(yàn)測(cè)量網(wǎng)板參數(shù)定義
三分力:升力FL、阻力FD、俯仰力矩M(繞支點(diǎn)),同時(shí)測(cè)出壓力中心點(diǎn)離網(wǎng)板前端距離d=e-(M/N)[9],(N為法向力)。
以上公式中空氣密度 ρ=1.225 kg·m-3,S為網(wǎng)板投影面積(m2),L為網(wǎng)板翼弦長(zhǎng)(m)。
所有試驗(yàn)數(shù)據(jù)都進(jìn)行了支架干擾修正,支架干擾修正采用直接扣除光支桿的方法來(lái)完成。
試驗(yàn)獲得網(wǎng)板模型的阻力系數(shù)Cx、升力系數(shù)Cy、俯仰力矩系數(shù)Cm與壓力中心系數(shù)Cp。優(yōu)化網(wǎng)板的水動(dòng)力性能主要是提高Cy,降低Cx并保證其穩(wěn)性,網(wǎng)板的穩(wěn)性可以通過(guò)網(wǎng)板的Cm與Cp來(lái)分析比較[21]。將Cy與Cx進(jìn)行比值處理,獲得的數(shù)值Cy/Cx即為升阻比,也是判定網(wǎng)板水動(dòng)力性能優(yōu)劣的重要因子[19]。為了清楚地分析4塊網(wǎng)板模型的水動(dòng)力性能差異,將試驗(yàn)數(shù)據(jù)分組并制成 Cx—α,Cy—α,C y/Cx—α曲線圖,見(jiàn)圖 5。
圖5中Cx—α與Cy—α曲線圖分別表示了4塊網(wǎng)板模型的阻力系數(shù)Cx與升力系數(shù)Cy隨迎流沖角α的變化曲線。在沖角大于20°之后,Cx與α基本成正比關(guān)系,2號(hào)網(wǎng)板模型的Cx較高;同時(shí)2號(hào)網(wǎng)板模型的Cy在α角度35°之前較高,最大升力系數(shù)為 1.687(α=35°),3號(hào)網(wǎng)板模型的最大升力系數(shù)最高,為 1.946(α=47.5°)。分析表明具有凸梯形結(jié)構(gòu)導(dǎo)流板的網(wǎng)板可產(chǎn)生較高的升力。
圖5中 Cy/Cx—α曲線顯示在沖角 α<22.5°時(shí),1號(hào)與2號(hào)網(wǎng)板模型的升阻比Cy/Cx較高,最大升阻比分別為6.507(α=22.5°)和6.328(α=22.5°),3號(hào)網(wǎng)板模型具有較高的最大升阻比,為7.486(α=30°)。分析表明,網(wǎng)板的導(dǎo)流板形狀為凸梯形可以獲得較高的升阻比。
網(wǎng)板的穩(wěn)定性是指網(wǎng)板的動(dòng)穩(wěn)定性,包括動(dòng)力穩(wěn)定和靜力穩(wěn)定,主要是指網(wǎng)板在作業(yè)沖角前進(jìn)時(shí),不易產(chǎn)生側(cè)翻和傾倒,且在網(wǎng)板傾斜甚至傾倒的狀態(tài)下具有恢復(fù)工作狀態(tài)的能力[18-19]。網(wǎng)板穩(wěn)性的分析方法有多種,根據(jù)楊吝[17,22]譯作,可以通過(guò)俯仰力矩系數(shù)和壓力中心系數(shù)分析網(wǎng)板的穩(wěn)性。
圖5 網(wǎng)板模型各自C x,C y及 C y/C x與沖角的關(guān)系Fig.5 Changing curve grouping com parison of C x,C y and C y/C x along w ith the angle of attackαchanged for otter board models
俯仰力矩也稱縱向力矩,是指作用在網(wǎng)板模型的空氣動(dòng)力對(duì)其重心所產(chǎn)生的力矩沿橫軸的分量,一般轉(zhuǎn)換為俯仰力矩系數(shù)Cm來(lái)分析比較。俯仰力矩可分為上俯仰力矩與下俯仰力矩,一般通過(guò)正負(fù)區(qū)分,圖中看出Cm值存在正負(fù),其絕對(duì)值的大小表示了俯仰力矩的高低,一般俯仰力矩系數(shù)越趨于0時(shí)表示該網(wǎng)板的俯仰穩(wěn)性越優(yōu),比較網(wǎng)板作業(yè)沖角對(duì)應(yīng)的Cm絕對(duì)值即可判斷網(wǎng)板穩(wěn)性高低,這里可根據(jù)各網(wǎng)板模型最大升阻比Cy/Cx對(duì)應(yīng)沖角α?xí)r的Cm絕對(duì)值來(lái)進(jìn)行判斷,具體數(shù)據(jù)見(jiàn)表2,2號(hào)網(wǎng)板模型在最大升阻比Cy/Cx對(duì)應(yīng)沖角α?xí)r的Cm絕對(duì)值最低,為0.061,穩(wěn)性較好。
表2 4塊網(wǎng)板模型最大升阻比對(duì)應(yīng)沖角α?xí)r的C m絕對(duì)值Tab.2 Absolute value C m at the angle of attackαcorresponding themaximum lift-drag ratio of 4 otter board models
利用壓力中心系數(shù)來(lái)判斷網(wǎng)板穩(wěn)性一般是通過(guò)分析最大升阻比時(shí)沖角前后5°范圍之內(nèi)的Cp變異系數(shù)來(lái)比較,該系數(shù)越小,網(wǎng)板穩(wěn)性越好[22]。計(jì)算所得數(shù)據(jù)見(jiàn)表3,2號(hào)網(wǎng)板模型的Cp變異系數(shù)最低,為4.43%。
表3 4塊網(wǎng)板模型最大升阻比時(shí)沖角前后5°范圍C p變異系數(shù)Tab.3 Variable coefficient of C p at the range of 5°before and after the angle of attackα corresponding themaximum lift-drag ratio of 4 otter board m odels
通過(guò)上述兩種方法對(duì)4塊網(wǎng)板模型的穩(wěn)性進(jìn)行比較分析,得出的結(jié)論均表明具有扇形導(dǎo)流板結(jié)構(gòu)的網(wǎng)板具備較好的穩(wěn)性。
網(wǎng)板模型風(fēng)洞試驗(yàn)是網(wǎng)板水動(dòng)力性能研究的方法之一,影響網(wǎng)板水動(dòng)力性能的試驗(yàn)設(shè)計(jì)因素也較多,如展弦比、面板數(shù)量、縫口寬度、面板曲率、V型折角等[19-21],常用的基礎(chǔ)研究方法是改變網(wǎng)板結(jié)構(gòu)的1個(gè)結(jié)構(gòu)參數(shù)設(shè)計(jì)試驗(yàn)[1,7-8,23-24],或改變多個(gè)參數(shù)開(kāi)展試驗(yàn)[2-4,9],在確定結(jié)構(gòu)參數(shù)時(shí),可開(kāi)展模型試驗(yàn)測(cè)試驗(yàn)證其性能[16-17,25-26]。開(kāi)縫式網(wǎng)板的導(dǎo)流板可以通過(guò)導(dǎo)引水流,調(diào)整網(wǎng)板的水阻力和擴(kuò)張力[18,27],本試驗(yàn)設(shè)計(jì)為單因素試驗(yàn),即通過(guò)改變導(dǎo)流板形狀來(lái)分析4塊網(wǎng)板模型的水動(dòng)力性能差異,為網(wǎng)板型式結(jié)構(gòu)的優(yōu)化提供參考。
網(wǎng)板的升力也即擴(kuò)張力,來(lái)自于網(wǎng)板受迎流作用時(shí)在垂直來(lái)流方向上產(chǎn)生的分力,用于擴(kuò)張拖網(wǎng)網(wǎng)口。試驗(yàn)表明,4塊網(wǎng)板模型的最大升力系數(shù)為Cy(凸梯形)>Cy(矩形)>Cy(扇形)>Cy(凹梯形),從導(dǎo)流板形狀分析來(lái)看,導(dǎo)流板面積分布越趨向中心,則產(chǎn)生的升力越大,樸倉(cāng)斗等[4]在研究網(wǎng)板面板的后退角Λ中發(fā)現(xiàn),后退角的適當(dāng)增加可以提高網(wǎng)板的升力系數(shù),其結(jié)果分析與葉板的面積分布有一定關(guān)系。目前實(shí)際應(yīng)用的網(wǎng)板有較多采用此種結(jié)構(gòu)的葉板結(jié)構(gòu),以提高網(wǎng)板材料的利用效率,獲得較高的網(wǎng)板擴(kuò)張力。
網(wǎng)板的水阻力,即網(wǎng)板拖曳前行時(shí)受到的迎流向阻力,為便于對(duì)比,選取作業(yè)沖角α=30°對(duì)應(yīng)的4塊模型網(wǎng)板的Cx值進(jìn)行對(duì)比,此沖角對(duì)應(yīng)各模型網(wǎng)板的升阻比較高,可以作為理論作業(yè)沖角[19-20]。數(shù)據(jù)表明,Cx(扇形)>Cx(矩形)>Cx(凹梯形)>Cx(凸梯形),具有凸梯形結(jié)構(gòu)導(dǎo)流板的網(wǎng)板模型阻力系數(shù)最低,可見(jiàn)導(dǎo)流板后部凸梯形結(jié)構(gòu)可以改善面板背部流態(tài),使網(wǎng)板阻力降低[16]。
網(wǎng)板的升阻比也可以稱為網(wǎng)板工作效率,具備良好工作效率的網(wǎng)板可以在降低網(wǎng)板阻力的同時(shí)提高網(wǎng)板擴(kuò)張力。試驗(yàn)表明,Cy/Cx(凸梯形)>Cy/Cx(矩形)>Cy/Cx(扇形)>Cy/Cx(凹梯形),可見(jiàn),凸梯形結(jié)構(gòu)的導(dǎo)流板設(shè)計(jì)具有較高的升阻比,即合理增加導(dǎo)流板中心面積的分布可以改善網(wǎng)板背部流態(tài),提高網(wǎng)板工作效率[4]。
網(wǎng)板的作業(yè)穩(wěn)定性也非常重要,在拖網(wǎng)拖曳過(guò)程中,網(wǎng)板在工作沖角時(shí)不會(huì)前后左右晃動(dòng)以保證網(wǎng)板的工作效率[13]。本文采用2種方法分析4塊網(wǎng)板模型的穩(wěn)性,結(jié)論表明具有圓弧導(dǎo)流板結(jié)構(gòu)網(wǎng)板模型的穩(wěn)性較優(yōu),對(duì)比矩形結(jié)構(gòu)網(wǎng)板,圓形葉板的網(wǎng)板更適宜在高低不平的海底拖曳[11]。
本試驗(yàn)研究得出,具有凸梯形導(dǎo)流板結(jié)構(gòu)的雙開(kāi)縫曲面網(wǎng)板具有較高的升力系數(shù),同時(shí)具有較大的升阻比,該形狀導(dǎo)流板設(shè)計(jì)可以改良雙開(kāi)縫曲面網(wǎng)板的水動(dòng)力性能。試驗(yàn)結(jié)果也表明具有扇形形狀導(dǎo)流板的網(wǎng)板穩(wěn)性較好,說(shuō)明導(dǎo)流板的后部采用平滑的扇面弧形結(jié)構(gòu)可以適當(dāng)提高雙開(kāi)縫曲面網(wǎng)板的整體穩(wěn)性。本試驗(yàn)的研究結(jié)果可以為不同型式網(wǎng)板的結(jié)構(gòu)設(shè)計(jì)提供一定參考。
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Research of deflector shape on hydrodynam ic performances of double-slotted cambered otter-board
WANG Lei,WANG Lu-min,F(xiàn)ENG Chun-lei,ZHANG Xun,ZHOU Ai-zhong,ZHANG Yu,LIU Yong-li,QIGuang-rui
(Key Laboratory of Oceanic and Polar Fisheries,Ministry of Agriculture;East China Sea Fisheries Research Institute,Chinese Academy of Fishery Sciences,Shanghai 200090,China)
In order to improve the hydrodynamic performance of double-slotted cambered otter board by optimizing the deflector structure,the effect of the deflector shape of double-slotted cambered otter board on hydrodynamic performanceswas investigated bymodel wind tunnel test.Four deflector shapes were designed in otter-board models:rectangle,fan shape,convex trapezoid and concave trapezoid.The basic structural parameters of four otter-board modelswere the same,the aspect ratio was 2.5,the camber ratio was 12%,the angle of double-layer deflector was 30°and 25°,and the angle ofmain-panel was 12°.The otter-boards modelswere installed on the six-componentmechanical tower-balance separately,and the testwas conducted in wind tunnelwith the flow velocity at28 m·s-1and the angle of attackαmeasured from 0°to 70°to obtain drag coefficients Cx,lift coefficient Cy,pressure-center coefficient Cp,calculated lift to drag ratio Cy/Cxand to give the relation curve of these values and angle of attackα.For comparison in the lift coefficient of four otter-board models,the results showed that the relationship of the maximum lift coefficient Cybetween four otter-board modelswas Cy(convex trapezoid)>Cy(rectangle)>Cy(fan shape)>Cy(concave trapezoid),themaximum lift coefficient Cyof the otter-board modelwith convex trapezoid structure was higher,itwas 1.946(α=47.5°).For comparison in the drag coefficient of four otter-board models,the results showed that the relationship of the drag coefficient Cxbetween four otter-boardmodels at the attack angel of30°was Cx(fan shape)>Cx(rectangle)>Cx(concave trapezoid)>Cx(convex trapezoid),the drag coefficient Cxof the otter-board modelwith convex trapezoid structure was lower.For comparison in the lift to drag ratio of four otter-board models,the results showed that the relationship of the maximum lift to drag ratio Cy/Cxbetween four otter-board modelswas Cy/Cx(convex trapezoid) >Cy/Cx(rectangle)>Cy/Cx(fan shape)>Cy/Cx(concave trapezoid),the maximum lift to drag ratio Cy/Cxof the otter-board model with convex trapezoid structure was higher,it was 7.486(α=30°).In comparison of stability,the stability of otter board model with double fan deflector structure was better,and its lower absolute value of Cmand variable coefficient Cpwere 0.061 and 5.43%respectively.Therefore,the double-slotted cambered otter-board with convex trapezoidal deflector could provide larger lift and have good working effect,the double-slotted cambered otterboard with fan shaped deflector had the higher stability.The resultswould offer the reference for the structural optimization design of trawl otter board.
otter board;wind tunnel test;hydrodynamic performances;deflector
S 971.4
A
1004-2490(2017)06-0682-08
2017-05-08
國(guó)家科技支撐計(jì)劃資助項(xiàng)目(2013BAD13B03)
王 磊(1980-),男,助理研究員,碩士,研究方向:漁業(yè)工程。E-mail:Emperor0228@163.com
張 勛,研究員。E-mail:zhangxun007@hotmail.com